Family members say a woman, her son and her boyfriend are believed among the four who died.

Investigators Tuesday continued to comb through the wreckage of the Emmaus apartment duplex that was destroyed by fire, killing four people.

The Lehigh County Coroner's Office is conducting autopsies and may need a day or two before details can be released. Fire officials referred calls to borough police, who have not released any new information.

The Lehigh County district attorney said early indications are that Sunday's blaze did not appear to be arson.

Melissa Twining, 48, her boyfriend, David, and her 16-year-old son, Montana, are believed to be three of those killed in the fire at 36-38 S. Fifth St., according to Melissa's sister, Valerie Twining of Catawissa, Columbia County.

"This morning, my father [Jacob Twining] called me," Valerie said. "He wanted me to know that my sister Robin just called him, and the coroner's office wanted Robin to help identify the bodies."

Jacob Twining and Robin Twining live in Pen Argyl.

Valerie said there were five sisters in the Twining family. She noted that Melissa went to Liberty High School in Bethlehem.

Valerie did not know David's last name, and officials have not officially identified any of the dead. The fourth victim is an unidentified woman, neighbors said.

Officials have said they were awaiting autopsy results before they name the victims of the borough's deadliest fire in recent memory.

East Penn School District Superintendent Thomas L. Seidenberger said a student is missing because of the fire and five other students were among those injured, displaced or otherwise affected by the fire.

Montana Twining was an East Penn student.

"Our prayers are with all those folks that were involved in that fire," Seidenberger said.

At the Emmaus Borough Council meeting Monday night, Emmaus High School's student representative, Rowan Hobson, a junior, said Montana's schoolmates are grieving his loss.

"Everybody at school is sad," Hobson said. "He was such a smiley person, a great kid. He had a lot of friends at Emmaus High School."

Earlier Monday, Michelle Richie Twining of Effort, Monroe County, revealed that Melissa Twining and Montana were two of the victims.

"Keep us in your prayers," she said in a Facebook post. "My sister [and] nephew died in an Emmaus fire. Just found out this morning. He just turned 16 last month."

Neighbor Roger Bean, 72, also remembered the Twinings.

"I don't know how they could have got out of there," Bean said Monday morning as he returned to Fifth Street to pick up a change of clothing and his medication.

The house, a three-story former funeral home that was converted into five apartments nearly 30 years ago, is likely to fall to the wrecking ball soon. The roof had collapsed and the left side of the facade had buckled on the top floors.

On Monday, dozens of motorists and pedestrians paused for a look, as a state police fire marshal and other officials pored over the wreckage, seeking clues to the cause. District Attorney Jim Martin said there were no immediate indications the blaze was suspicious. He said the investigation is continuing.

The fire broke out about noon Sunday and moved with terrible speed, sending up a thick pall of choking black smoke.

Neighbor Michael Aldinger said he cleared one of the bottom-floor apartments before helping a man from an upper-floor apartment down from the roof. Aldinger said he could hear a woman screaming inside the house but was unable to reach her.

"I wish I could've done more," he said, adding that the man he helped worked at a local McDonald's restaurant and was disabled.

Others identified the disabled man as Bobby and said his girlfriend, whom they knew as Marie or Maria, was among the dead.

"Bobby looked after her. She had some medical issues," said Erica Henningsen, a Wescosville woman who said she used to work with Bobby at McDonald's.

"They've been together for years," she added.

Employees at the restaurant confirmed that a co-worker named Bobby was among the survivors of the blaze but were not allowed to say more.

Many of the displaced residents, including Bean, were put up at hotels in Allentown.

Bean said he remembers hearing explosions and screams from two women who made it out safely from the building.

He said he thinks the explosions were caused by oxygen tanks that one of the victims used.

"The second explosion — that one really cracked," Bean said. "Glass flew to the other side of the street."

He said two of the victims lived on the third floor, and the two others on the second. Those living in the three other units made it out safely. The building, owned by Michael and Loretta Boyko of Macungie, had not been inspected since 2005, according to paperwork on file with the borough.

Zoning director James Farnsworth said the borough requires owners and landlords to arrange for inspections every time there is a change of occupancy. It was unclear whether new tenants had moved in since the 2005 inspection, which the building passed.